The field of the invention is that of heaters for fuel being furnished to an internal combustion engine cylinder and the invention relates, more particularly, to heating of fuel furnished to a cylinder by a fuel injector to facilitate mixing of the fuel with air being supplied to the cylinder.
The invention relates to an injection internal combustion engine with electric spark ignition, comprising at least one cylinder provided with an air inlet channel, at least one inlet valve fitted in the cylinder head, at least one fuel injector with a heating element with heat sink fitted downstream of said injector, and at least one PTC wafer provided thereon.
Such an internal combustion engine is known from German Patent No. 3,426,469-C2 and U.S. Pat. No. 4,967,706.
It has been found that approximately 50% of the total exhaust gas pollutant emission is formed in the short period during which the engine has not yet reached its operating temperature. Even exhaust gas catalytic converters, which in normal circumstances reduce the exhaust gas pollution emission by approximately 90% reach this degree of conversion only when the operating temperature of the catalytic converter has been reached. The conversion begins at a temperature of approximately 300.degree. C., so that for a significant time after a cold start there is little or no reduction at all in the exhaust gas pollution emission of the engine in a catalytic converter. Since the temperature level is not high enough to vaporize all of the gasoline or alcohol, fuel, an additional or extra quantity of fuel has to be added when the engine is cold in order to obtain a desired combustible air-fuel mixture ratio. This leads to a high exhaust gas pollution emission. At low engine temperature both the fuel consumption and the exhaust gas pollution emission are therefore relatively high. Heating the fuel/air mixture therefore makes a considerable contribution to the improvement of the environment and also achieves a considerable fuel saving, by permitting less fuel (or no additional or extra fuel) to be injected. The fuel in the internal combustion engine mentioned above is preferably sprayed onto a heating element, which heating element is brought to the desired temperature in a short time, and is therefore adapted to bring the fuel to a desired temperature in the process. The fuel will thereby vaporize better and better mixing with the combustion air is also achieved. The heating element is preferably switched off when the engine is hot enough to take over the vaporization of the fuel.
In the case of the engine known from the above mentioned German Patent 3426469-C2 the heating element is designed in the form of a pipe projecting into the inlet channel of the cylinder and surrounded by an insulating tube. The pipe and the tube are provided with an end flange lying in a recess of the cylinder head and fixed in alignment with air flow through the air inlet pipe. A disadvantage of this engine is that fitting and replacement of the heating element is a time-consuming job. The same objection applies to the engine according to the above-noted U.S. patent wherein the heating element is integrated in a plate wedged between the inlet channel and the cylinder head. Those known engines also have a tendency to provide a reduced air inlet cross-section.